Informant describes an optical illusion creating the appearance of a hill on which the rules of gravity don’t appear to apply in the conventional sense. Cars left in neutral roll up instead of down, water trickles up, etc. The kids in the neighborhood would say that a group of children getting killed or something of that nature is what gave the hill its unnatural properties, though the informant doesn’t buy into those explanations, instead calling it an illusion but not elaborating on how exactly it’s caused.
Informant speaks of multiple “gravity hills” in various locations around the world, likely wherever the conditions for the illusion arise. I’ve heard of these as well (possibly on an episode of Mythbusters or the like) and don’t find it strange at all that such an illusion would cause quite a stir in those prone to belief in supernatural phenomena.